Setting tyre pressures at this time of year can be affected by the ambient temperature, the following advice is from Michelin and may bad useful for those experimenting with pressures

Quote:

When it gets colder, your tyre pressure drops. If a tyre is inflated to 2 bar (29psi) at 20°C, for example, the pressure may only read 1.8 bar (26psi) at 0°C. If your tyre pressures are low when you check them in cold weather, re-inflate them to the vehicle manufacturers’ recommendations.
Cold weather tyre pressure
Our advice:

When setting your pressures with cold tyres (tyre temperature at the outside ambient temperature), set them to the vehicle manufacturers’ recommended pressures.
If you set your pressures in a warm garage or workshop, add 0.2 bar (3psi) to the vehicle manufacturers’ recommended pressures. This will ensure that you compensate for the cold temperature and run at the correct pressures.